Method of and apparatus for sorting bodies of ferromagnetic materials in magnetic field



O Unlted States Patent 1111 3,539,005

72 Inventor Pavel Nekvlndl 51 Int. c1 B07c 5/344 Llberee, Czechoslovakia [50] Field of Search 209/1 1 1.8, [21] Appl. No 790,905 81.1, 81, 73. 74; 324 41 [22] Filed Jan. 14, 1969 [45] Patented Nov. 10, 1970 References Cited [7 3] Asaignee Stltni Vylkumny Ustav Textilni UNITED STATES PATENTS Libemflmlmhvlkil 2.822,088 2/1958 Beaumont et al..... 209/s1.1 1 Pflomy 3,392,830 2/1968 Broderick e181. 209/74x a Primary Examiner-Allen N. Knowles Assistant Examiner-Gene A. Church AttorneyMichael S. Striker [54] METHOD OF AND APPARATUS FOR SORTING ABSTRACT Fermma gnetlc articles are conveyed through MAGNETIC MATERIALS IN zones of different magnetic field intensity; in each zone their m cm 3 D permeability is compared to a standard value. Signals indicating coincidence with, or deviation from such standard value [52] US. Cl. 209/73, operate a mechanical sorting device which separates articles of different permeability for collection in different containers.

METHOD OFAND APPARATUS FOR SORTING BODIES OF FERROMAGNETIC MATERIALS IN MAGNETIC IELD BACKGROUND OF THE INVENTION The present invention relates to a method of sorting ferromagnetic articles according to their permeability. The permeability and hardness of ferromagnetic material are inversely proportional to one another and, based on such recognition, the present invention provides a convenient nondestructive way of classifying articles such as ball or roller bearings, travellers on a ring spinning machine, and the like.

In a conventional method of sorting articles made from ferromagnetic material, which is based on discrimination in a magnetic field, the articles to be examined are inserted in the primary coil of an air core transformer. The thus introduced articles change the magnetic field and induce an electromotive force in the circuit of the secondary coil of the transformer. I

A drawback of such conventional method is that it furnishes an either/or response and does not discriminate between permeabilities which are higher or lower than those corresponding to a predetermined standard. It only rejects or accepts articles of certain permeability, but does not grade them within a range of values.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a simple method of sorting ferromagnetic articles in a mag- These objectsare accomplished by conveying articles made of ferromagnetic material along a predetermined path crossing a series of zones of predetermined and differing magnetic field intensity provided in a non-homogenous magnetic field. For each zone the induced electromotive force is-compared with a standard value, to indicate whether an article has the standard permeability predetermined for the particular zone. If it has the required permeability, a preferably mechanical sorting device is actuated to remove the article from the respective zone and to collect it in a corresponding receptacle. If does not have the permeability corresponding to a predetermined value, the article is advanced into the next adjacent zone of different magnetic intensity, where another comparison between the obtained electromotive force, the field intensity and the permeability takes place, and so on, until coincidence of the measured and predetermined permeability values triggers the sorting mechanism for removing the article and introducing it into one of several receptacles provided for articles of higheror lower permeability.

The magnitude of the induced electromotive force is the same when an article of relatively weak permeability passes through a zone of greater field intensity, as when an article of relatively strong permeability passes through a zone of lesser field intensity. If the sequence of zones is such that the articles pass first through a zone of least intensity, articles with strong permeability will induce therein an electromotive force which an article of lesser permeability will 'not induce until it has been conveyed into a zone of greater field intensity.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

DESCRIPTION OF THE DRAWING FIG. 1 is a somewhat schematic fragmentary front elevational view of the apparatus which is employed for the practice of the above described method;

FIG. 2 is a sectional view as seen from the line Il-II of FIG. 1; and

FIG. 3 is a wiring diagram of the circuit used in the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a measuring coil 1 connected to a source of current, on the U-shaped core 2 on which two pole pieces 3 face each other across an air gap 4. As shown in FIG. 2, the air gap 4 has a trapezoidal cross section defined by the slant of the pole pieces 3 which are furthest apart from one another at the outer face of the core 2, and taper off toward each other in theinterior region of the core 2. The maximum width of the air gap 4 corresponds to a zone of least magnetic field intensity, and conversely, the minimum width corresponds to a zone of greatest magnetic field intensity.

The air gap 4 forms a passageway for articles whose permeability is to be examined and which, in the illustrated example, are travellers 5 of a ring spinning machine. The travellers 5 are placed in radial grooves 6 of a conveyor wheel 7 and are advanced, by the rotation of the wheel, along an arcuate path which intersects the air gap 4 where a retaining device or trap plate 8 on one arm of a two-armed lever 9, prevents their falling off. The other arm of the lever is attached to an armature 10 which is connected to spring means 12 for removal from an electromagnet 11 when the latter is deenergized.

The measuring coil 1 is connected to a Wheatstone bridge 13; as shown in FIG. 3, which has a diagonal 17. This diagonal is also connected to the electromagnet 1].

The operation of the apparatus is as follows:

When a traveller 5 is conveyed across the air gap 4 in the direction of the arrow 18 shown in FIG. 2, a rectification and change in the magnetic flux of the circuit is produced, which is registered as a change of the inductivity of the measuring coil 1, and which is proportional to the permeability of the material of which the article is made, as well as to its relative position in the magnetic field. Calculation of the inductivity of the coil, respectively, of the induced electromotive force, takes onto account the fact that on entering the air gap 4 an article exerts less of an influence on the magnetic flux than on leaving, since in the latter event the article occupies almost the entire downstream part of the air gap.

The Wheatstone bridge 13 to which the measuring coil 1 is connected is adjustable through the impedances 14, 15 and 16, to be in equilibrium when, for example, a traveller 5 of predetermined hardness that is, permeability, is at the halfway point of its passage through the air gap 4. The equilibrium state of the bridge 13 is coordinated with a zero voltage on the diagonal 17. The zero voltage, in turn is a signal of deenergization of the electromagnet 11 connected to the diagonal 17, whereby the armature 10 is released from the electromagnet, and withdrawn therefrom by the spring means 12. The movement of the armature 10 causes the lever 9 to tilt the trap plate 8 so that a suitably positioned container (not shown) can receive the traveller as it falls out of the groove 6.

If a traveller 5 entering the air gap 4 has a permeability which is greater than the standard value, that is, if the material of which the article is made has less hardness than is specified, the traveller will not reach the half-way mark but will have been removed before getting to that point; greater permeability, that is lesser hardness causes the predetermined zero voltage to be registered when the traveller is in a zone close to the widest diameter of the air gap. At that stage the trap plate 8 is actuated by the zero voltage, and causes articles of greater than standard permeability to enter another container. Conversely, articles of less than standard permeability will be conveyed beyond the half-way mark and close to the narrow end of the trapezoidal air gap before the zero voltage corresponding to the magnitude of the induced electromotive force will cause the trap plate to swing away and cause articles of less than standard permeability to enter a further container.

lt will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of methods of and apparatus for sorting articles made of ferromagnetic material in a magnetic field differing from the types described above.

While the invention has been illustrated and described as embodied in a method of and apparatus for sorting articles made of ferromagnetic material in a magnetic field, it is not intended to be limited to the details shown, since various modification and structural changes may be made without departing in any way from the spirit ofthe present invention.-

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, front the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range ofequivalence ofthe following claims.

I claim:

1. A method of sorting magnetizable articles, comprising the steps of establishing a magnetic field including a succession of zones each of which has a predetermined intensity; conveying a series of magnetizable articles of different permeability along a path which intersects successive zones of said field whereby each article produces in the magnetic flux across said zones a change which is a function of its permeability; measuring said changes of magnetic flux and determin ing the deviation of such changes for each zone of said field with a different reference value; and sorting the articles in accordance with the extent ofsuch deviation.

2. A method as defined in claim 1, wherein said sorting step comprises removing articles of different permeability from different portions ofsaid path.

3. A method as defined in claim I, wherein said zones include two outermost zones and the intensity of said magnetic field varies gradually between said outermost zones thereof.

4. A method as defined in claim 1, wherein said path is an arcuate path.

5. A method as defined in claim 1, wherein the intensity of said field increases in the direction of travel of articles along said path.

6. A method as defined in claim 1, wherein said sorting step comprises removing articles from those portions of said path which intersects zones wherein the respective article causes in the magnetic flux a change whose deviation from the respective reference value corresponds to a predetermined magnitude.

7. Apparatus for sorting magnetizable articles, comprising means for establishing a magnetic field including a succession of zones each of which has a predetermined intensity; conveyor means for transporting a series of magnetizable articles of different permeability along a path which intersects successive zones of said field whereby each article produces in the magnetic flux across said zones a change which is a function of its permeability; means for measuring said changes of magnetic flux and for determining the deviation of such changes for each zone of said field from a different reference value; and means for sorting the articles in accordance with the extent of such deviation.

8. Apparatus as defined in claim 7, wherein said means for establishing a magnetic field comprises a measuring coil having a core provided with convergent pole pieces defining an air gap and flanking said zones, said measuring means comprising an electric control circuit arranged to produce signals for said sorting means.

9. Apparatus as defined in claim 8, wherein said sorting means comprises mechanical sorting means.

10. Apparatus as defined in claim 7, wherein said circuit comprises a resistance bridge including impcdances adjusted to establish an e uilibrium of the bridge when articles having a nominal permea ihty are located m a predetermined zone of said field.

11. Apparatus as defined in claim 10, wherein said sorting means comprises an electromagnet and a mechanical sorting device operative in response to a change in the condition of said clectromagnet in response to said signals.

12. Apparatus as defined in claim 11, wherein said electromagnet is connected to a diagonal of said bridge and wherein said sorting means comprises a retaining member for articles on said conveyor means, said retaining member being movable from retaining position in response to said change in the condition of said electromagnet. 

